Component Buyer's Guide - Techniques and Tips

ACOUSTICAL TREATMENTS

Also remember that just because an OEM tweeter is mounted in the A-pillar with the midrange low in the door or kick panel doesn't mean that is where it will really sound the best. While the highest frequencies will seem to be high up above the dash, the overall sound will probably not be coherent across the audible frequency range, especially around the crossover frequency, and it will be difficult to make the system sound its best. Even if mounting the tweeter close to the midrange will place it low in the door or kick panel area, in most every case, it will sound better there with minimal effort, than if they are separated.

Even when the mounting structure is built solid, any areas around and behind the speaker need to be treated so that they do not resonate or vibrate and detract from the sound we want to hear. A number of sound deadening and damping materials from any of several manufacturers can handle this. Metal panel vibrations, as can occur with door outer and inner panels, can be controlled with adhesive-backed mass damping materials. Adhesive-backed absorptive foam and/or reflection-controlling silicone rubber materials can be used to attenuate and control the back wave from the speaker cone, preventing it from reflecting off hard surfaces behind the speaker and then coming through the cone, causing distortion.

MIDRANGE/TWEETER MOUNTING PROXIMITY

Sure, if you are using some serious processing power and have many hours to design the system, you can make it sound really good with the speakers separated. But we're talking about making systems sound good without extensive vehicular modifications, thousands of dollars and many hours in the install bay.

So, if the midrange speakers don't sound good, then it's very likely that the entire system will not sound good either. And ensuring that they sound good is in large part determined by the quality of their installation. While a midrange or midbass speaker isn't as large as a subwoofer, it still must be very solidly mounted. The moving mass of the speaker cone, especially at high output levels, will try to move the entire speaker, and the surface it's mounted to. If it's not mounted properly on a solid, non-resonant surface, it may cause parts of the mounting surface to rattle, buzz and cause unwanted noise and distortion.

The number one question regarding high-frequency speaker placement is, "Where does the tweeter go, relative to the midrange?"

Once the system is tweaked with the midrange and tweeter close together, if there is the desire to raise the overall soundstage, a second set of tweeters can be used, carefully mounted higher in the A-pillars and crossed over very high (above 10,000 Hz). Done carefully, this can help with the apparent stage height, without detracting from sound quality of the primary midrange/tweeter system.

Conclusion

It's a good idea, if possible, to keep the midrange and tweeter close together. This will minimize problems caused by separating them by large distances. These problems include comb filtering and other frequency response problems, instruments and vocalists that seem to come from multiple locations, arrival time issues, etc. In general, separating the midrange and tweeter make it much more difficult to tune the system's overall sound quality response.

But what about the higher-frequency speakers: the midranges and tweeters? In most installations, much less attention is paid to these speakers than to the subwoofers. In fact, many systems that do produce good low-frequency response from the subwoofers do not produce the same performance from the rest of the speakers in the system, quite often because the midrange and tweeter speakers are poorly installed, severely limiting the system's true sound quality potential. But with just a little additional effort in the installation of these speakers, the system can sound really good.

These are just a few techniques, tips and guidelines that can help make your system sound its very best. While it may not be possible to accomplish all of these things in every installation, the more effort that can be put into the installation, the better the system will likely sound.

In fact, quite often, a good speaker choice is a set of properly designed coaxial speakers. They can sound very good, with very minimal effort. With coax speaker designs, the speaker manufacturers know exactly where the tweeter will be relative to the midrange, and the system can be designed more critically. With even the best quality separates, the manufacturer must make assumptions about where the tweeter will be mounted, and if they are not installed accordingly, the speaker system's response may not be optimized.

Of course, you can go to the most extreme levels for speaker installation, spending hundreds of hours on the design, fabrication and detail when building an ultra high-end system for sound quality competition, for example. But in the real world, for those of us who simply want to upgrade our car audio systems so they sound good when we drive them every day, what are the minimum requirements to ensure that the speakers will sound their best?

We all know that subwoofers are really important and help provide the low frequency foundation in any system. But, the speakers reproducing the majority of the music in the range above the sub-bass range are what will truly determine how the system will really sound. Design and install the higher frequency speakers the right way, and the system will have the potential to sound awesome. Install them poorly, and there will be no possible way to make the system sound good.

For the purposes of this article, let's assume that everything in the audio system connected before the speakers will provide a clean, undistorted signal to the speaker, with sufficient power to reach the desired listening levels for the system. Also for our purposes, we're not going to excessively burden ourselves with optimizing the system for staging, imaging and other qualities that would require many, many hours to achieve. We're going to look only at the installation of the speakers themselves in a simple OEM speaker upgrade system design, and what it takes to achieve excellent frequency response, acceptable volume levels, minimal distortion, and eliminate annoying resonance and rattle issues, with minimal effort.

Material selection for these purposes can range from ABS plastic, to fiberglass, to aluminum, or even steel. For door installations, wood or MDF usually isn't a good choice because when it gets wet from rain, it can warp, swell, or break down and fall apart. And, backstrap or small thin brackets won't do much good either, as they cannot provide any real strength for the panel, or help seal large holes.

The sound quality improvement will be directly related to the quality and effort put into the structure. Build it right and it can sound great.